Why Maintenance Tasks are Important

Produced by

Joe Marchese

Why is it important to turn off the furnace and/or

air handler disconnect before inspecting the unit?

This is a safety concern – inspecting equipment with the

power on can cause injury to both the technician and the equipment.

Why is it important to visually inspect all

wire terminals and wires?Electrical systems that are overloaded will heat up and discolor the insulation

on the wiring. Discolored wiring is a sign of a system problem.

Also, loose connections may cause the system to draw more amperage.

These connections will eventually break, causing a system breakdown.

Why is it important to check thermostat

operation for accuracy? This ensures that the thermostat is

maintaining the right temperature for the customer. Most customers can feel a

3 to 5 degree difference in temperature.

Why is it important to check the cycle rate

switch(es) on the thermostat?

This ensures that the system is cycling on and off correctly,

with minimum temperature swings.

Why is it important to check the belt tension for proper adjustment?

A loose belt will cause slippage, which will cause the system to

deliver an improper amount of airflow.A belt that is too tight will

cause bearing wear.

Why is it important to visually inspect the belt, bearing and

pulley for signs of wear?

Signs of wear indicate that the parts need to be changed and

will fail in the future.

Why is it important to check the pulley and

drive alignment?

A misaligned pulley and drive may cause the belt to slip off, as well as

belt and pulley wear.

Why is it important to check the pulley and drive set screws for tightness?

Loose pulley and drive set screws will cause the pulley to slip, which will cause the CFM delivery to be reduced. This will cause damage to the shaft.

Why is it important to lubricate the motor

and fan bearings?

Premature bearing failure can be a result of a motor that is not lubricated as per the manufacturer’s schedule.

Why is it important to check the blower wheel

for dirt build-up?

Dirt build-up on the blower wheel will reduce the CFM delivery of the fan.

Why is it important to visually inspect the fan motor for bearing wear

by spinning the fan wheel?

A fan motor that stops quickly is a sign of bearing wear or no lubrication.

On an electric furnace, why is it important to check supply voltage?

Heating elements are rated for a specific range of voltages. Voltages

outside this range will not produce the rated BTU output for the furnace.

On an electric furnace, why is it important to check amperage on the main line as each heating element is

energized?

This ensures the heating element(s) are working.

On an electric furnace, why is it important to

check and record voltage after all heating elements

are energized?

A voltage drop of 5% or more when elements are energized is too high – electric line size may be too small.

On an electric furnace, why is it important to check the temperature rise through

the furnace and adjust fan speed (all furnaces)?

If a temperature rise occurs that is not within the specified range, this indicates that airflow delivered by the furnace is

not correct.

On a gas furnace, why is it important to remove and clean burners and check heat exchanger for cracks?

Dirty burners will cause incomplete combustion and will produce CO.

A cracked heat exchanger may cause CO to enter the living space.

On a gas furnace, why is it important to check burner

alignment to ensure no flame impingement is occurring

on the heat exchanger?

Any impinging of flame will create CO.

On a gas furnace, why is it important to remove,

clean and adjust the pilot assembly, where required?

A clogged pilot orifice may cause a weak pilot flame, which may cause the gas valve to fail to open on a call for heat.

On a gas furnace, why is it important to check and

record thermocouple output?

A thermocouple with a low output voltage will not be able to ‘hold in’ the gas valve.

On a gas furnace, why is it important to check and record

safety drop-out time?

This is a safety concern. If the pilot does not shut down when no flame is present, it will cause raw natural gas to enter the living space.

On a gas furnace, why is it important to check, record and adjust manifold gas pressure?

A misadjusted gas valve will cause incomplete combustion and

could cause the unit to produce CO.

On a gas furnace, why is it important to check the draft diverter for obstructions?

An obstruction in the diverter will cause products of combustion

to enter the living space.

On a gas furnace, why is it important to check and

record stack temperature and draft pressure?

If the stack temperature is insufficient, the products of combustion

will not be drawn up the chimney.

On a gas furnace, why is it important to

check and record CO2?

CO2 is an indication of the combustion efficiency.

On a gas furnace, why is it important to

check and record CO levels?

A high CO level is a very dangerous situation; the cause

must be determined and repaired.

On a gas furnace, why is it important to record and check high temperature

limit cut-out setting?

This is a safety item. If the furnace is running too hot,

the burners will shut down before there is a problem.

On a gas furnace, why is it important to check and record fan switch cut-in and cut-out

temperatures?If the fan cut-in is too high, the

unit could cycle on the limit switch; also it may cause undue stress

on the heat exchanger.If the fan cut-in or cut-out is too low, the customer may complain of cold drafts.

On an air conditioner, why is it important to inspect the condenser fan motor for

bearing wear?

A motor that slows down too quickly indicates a bearing problem.

On an air conditioner, why is it important to clean the condenser?

A dirty condenser will cause high discharge pressures and very inefficient operation.

On an air conditioner, why is it important to clean the evaporator?

A dirty evaporator will cause poor heat transfer and will cause the coil to frost up.

On an air conditioner, why is it important to

check and record voltage at the contactor?

Compressors are rated for a specific range of voltages. Voltages outside

this range will cause damage to the compressor’s motor.

On an air conditioner, why is it important to check and record voltage drop across the contactor?

This checks the contactor for signs of wear. There should be no voltage drop

across the contactor.

On an air conditioner, why is it important to check and record amperage draw on each hot leg?

A compressor running at amperages outside its rated values will likely fail.

On an air conditioner, why is it important to check and record the system’s head pressure?`

Higher than normal discharge pressure is an indication of a system problem.

On an air conditioner, why is it important to check

and record the system’s suction pressure?

Higher and lower than normal suction pressures are indications

of a system problem.

On an air conditioner, why is it important to check and record the system’s superheat at the

inlet of the compressor?

Superheat is one method of checking the refrigerant charge of a system.

On an air conditioner, why is it important to check and record the amount of subcooling at the outlet of the condenser?

Subcooling is one method of checking the refrigerant charge of a system.

On an air conditioner, why is it important to check

the temperature drop through the furnace or air handler?

If the temperature drop is not within the specified range, it is an indication that airflow delivered by the furnace

is not correct.

The

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